This invention is concerned with a tetrapeptide, L-2-ketopiperidine-6-carbonyl-L-histidyl-L-thiazolidine-4-carbonyl-.beta.- alaninamide (L-Kpc-L-His-L-Tca-.beta.-ala-NH.sub.2) or a pharmaceutically acceptable salt thereof which is useful as a central nervous system stimulant with a rapid onset of action and a minimum of adverse side effects.
Thyrotropin releasing hormone (TRH) is a naturally-occurring, well-known tripeptide, L-pyroglutamyl-L-histidyl-L-prolinamide. Besides its hormone releasing activity it is also known to have antidepressant activity.
Recently several publications have reported the preparation of derivatives and analogs of TRH with a view to augmenting the antidepressant activity of TRH. Veber et al., in U.S. Pat. No. 3,959,248, describes a group of compounds analagous to TRH which manifests an increased antidepressant activity and/or decreased hormone releasing activity. Belgian Pat. No. 832,783 describes a TRH derivative in which the amide nitrogen, proline amide, is substituted with a 2-carbamylethyl group resulting in the tetrapeptide amide, L-pyroglutamyl-L-histidyl-L-prolyl-.beta.- alaninamide which also manifests an increased antidepressant activity relative to the hormone releasing activity.
The novel compound of this invention, L-Kpc-L-His-L-Tca-.beta.-ala-NH.sub.2, displays greater activity as a central nervous system stimulant than does TRH.